becuz i think,rates can be made by some small trade (use 10$ to make 10 rates is possible).and honest traders list were posted by some one in forum(may be they have done trade before, may be its 1 of 10$ deals).

at last, what's the procedure of this selling? does it look like this?

1: i send him mt-gox usd2: he send me bank wire3: i wait,til i receive the amount (may be couple days after)4: done?

Inspect those 20 OTC ratings and see who has he traded with. 20 ratings with 1 point are different than 10 ratings with 1 point + 7 ratings with 5 points + 3 ratings with 9 points. Check who are that people that gave him higher ratings. If those people are also trusted then it's probably OK. More info here.

You can also follow his post history on the forum, see what trades has he made, etc.

Anyway: 20 OTC ratings over a large time period (several months) are usually a pretty good sign.